The present invention relates to a swivel coupling for connection and feedthrough of an electrical cable to and through a relatively rigid case or housing of a piece of electrical equipment, appliance or the like.
Swivel couplers are needed, generally speaking, wherever a piece of electrical equipment is to be electrically connected to a power source under conditions which must permit more or less random orientation of the equipment to the source. Thus, any equipment that is being handled will be moved in relation to the connection which includes turning. Such equipment, including particularly machine tools, may include extensive linkage, pivot couplers etc., to be passed through by electrical conductors. In all these cases, twisting of the cable or conductors must be avoided. Usually, the connectors or cables are held in some fashion at the housing, and these locations endanger the cable and conductors particularly because strong tension twisting forces may be exerted.
The German printed patent application No. 2,153,418 proposes a coupler that permits unrestricted turning. The particular connector includes a body incorporating a mechanism which permits relative turning of two parts. Electrical conductors lead into each of these parts, and U-shaped contact elements as well as contact pins provide slip ring like electrical connection. This coupler, therefore, has many individual parts. Moreover, the electrically active parts serve additionally as bearings and wear correspondingly.
The German printed patent application No. 2,511,294 discloses a plug element having embedded a rather strong annulus with a bead-like bulge serving as bearing element and sliding in a matching groove-like complementary part in the casing or housing being traversed. This ring or annulus is quite small and since the plug element itself is quite soft, positioning of the annulus is difficult. This, in turn, poses difficulties in making electrical connections because the distance between the end of the plug and the surface of the annulus is quite difficult to maintain. Also, du to softness of the plug, it may bend so that the distance between the several contact elements may irreversibly change, leading to failure in contact making.
Other known swivel connections of more or less complicated construction are shown, e.g., in U.S. Pat. Nos. 3,957,331, 3,950,052, and 3,937,543.